In the chemical industry and in particular that part of the chemical industry which deals with fluids packaged in tanks, or fluids passing through pipes, it has become the practice to determine the physical, or chemical spectra, and/or other characteristics of such fluids by passing light energy through the fluids. The loss of light energy, or a change in frequency of such light energy, provides evidentiary data, which enable the user to determine certain sought after parameters. In such arrangements, there is generally a transmitter probe and a receiving probe or multiples thereof. The probes are secured to the side of the tank, or on a pipe, or on a fluid container of some sort. A probe is not simply secured to the tank, or pipe, or fluid container, but has an end which enters the tank, or the like, to come in contact with the fluid, in order to transmit the light energy through the fluid. In the prior art, the probes have been made using a housing of stainless steel with a hollowed out cylinder formed therein. Into the hollowed out cylinder there is inserted a bundle of fiberglass optics. In the prior art, the bundle of fiberglass optics is secured to the stainless steel housing by an epoxy glue or mechanical interference fit or crimp. There are a number of problems with the prior art probes. For instance, when one of the prior art probes is located in a tank, and there is a great deal of fluid pressure against that probe a problem often develops. In response to the fluid pressure (in the foregoing situation) there is a "push" against the fiberglass optics which acts to "push" the fiberglass optics into the stainless steel housing, (i.e. out of the tank), thereby causing the probe to leak. In such cases it has been found that the epoxy glue has a strong affinity for the stainless steel but does not have a strong affinity for the bundle of fiberglass optics. Very often, in such cases, a tunnel, or a hollowed out cylinder, is formed in the epoxy glue and it is apparent that in the prior art the epoxy glue does not always hold the fiberglass optics against fluid pressure. Another problem, with the fiberglass optics arrangement, is that the glass does not give satisfactory transmission of light energy at certain frequencies. In addition fiberglass optics are susceptible to damage from certain fluid materials such as acids and the like. In this last mentioned regard it is true that a bundle of fiber optics provides voids (spaces between the fiber optics) which enable the fluids to enter into the bundle and do damage. Mechanical interference fit, or crimping, and/or epoxy application to windows in front of the fiber optics bundle were tried in order to minimize corrosion and pressure effects on fibers. However the probes formed by these methods are very limited because they leak at relatively low pressure. The present structure overcomes the infirmaties of the prior art light transmission probes.